Intelligent Earplug System

1. An earphone comprising: an earplug, a processor, a wireless interface, a battery, a speaker, and a sensor; wherein when the earphone is located in a user's ear, the sensor detects data indicative of the state of sleep of the user and provides that data to the processor, and the processor is configured to cause the speaker to provide sound to the user based on the sensor data.

2. The earphone of claim 1 , wherein the processor is configured to cause the speaker to provide a sound when the sensor data indicates that the user is in REM sleep.

3. The earphone of claim 2 , wherein the sensor comprises an accelerometer, and the determination that the user is in REM sleep is based on head movement detected by the accelerometer.

4. The earphone of claim 1 , wherein the sensor comprises one or more of a movement sensor, a temperature sensor, or a heart rate sensor.